feat: create Blazor-based login component with EmptyLayout

- Create Login.razor component at /login path with Blazor form
- Create EmptyLayout to prevent MainLayout wrapping on login page
- Update Program.cs to redirect unauthenticated users to /login (Blazor route)
- Integrate with CustomAuthenticationStateProvider for proper auth state management
- Handle authentication response and token storage

Note: Login flow still has routing issues - investigating dashboard redirect

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/dotnet/QuantEngine.Web/wwwroot/login.html

@@ -294,11 +294,28 @@
                 });
 
                 if (response.ok) {
-                    // 아이디 저장
+                    const data = await response.json();
+
+                    // 토큰 저장 (Blazor 인증 상태에 필요)
+                    if (data.accessToken) {
+                        localStorage.setItem('quant_admin_access_token', data.accessToken);
+                    }
+
+                    // 사용자 정보 저장
+                    if (data.username) {
+                        localStorage.setItem('quant_admin_username', data.username);
+                    }
+
+                    if (data.role) {
+                        localStorage.setItem('quant_admin_role', data.role);
+                    }
+
+                    // 아이디 자동입력 설정 저장
                     if (rememberUsername) {
-                        localStorage.setItem('quant_admin_username', username);
+                        localStorage.setItem('quant_admin_remember_username', 'true');
                     } else {
                         localStorage.removeItem('quant_admin_username');
+                        localStorage.setItem('quant_admin_remember_username', 'false');
                     }
 
                     // 대시보드로 이동